1. Statement of the Technical Field
Embodiments concern aligning two digital images, such as photos or maps, using a mobile device having a limited display area.
2. Description of the Related Art
There are several systems and methods available for aligning two images on a computing device. One example is Canon's PhotoStitch application which allows a user to “stitch” multiple images together to form a single, large size picture. The application merges two or more digital photographs allowing the user to select a point in one digital photo and drag a little thumbnail of the surrounding pixels over to another photo and line up the corresponding image features. This application was designed for use with Canon's digital camera line and is primarily used to create panoramic shots from separately shot images taken using camera functions such as Canon's Stitch Assist mode. This method works well when used on images taken from a similar, if not the same, orientation and zoom level. However this method fails to locate a general match where two images may have significantly different orientation or zoom level. Additionally, Canon's method is not suitable for use on small screens, such as those for smart phones and other small mobile devices.
Another method is utilized by the Maprika smart phone application. A user selects a point on a map image and a corresponding point on a digital map to geo-locate the map image. The application provides a user with a fixed target selection pattern and allows user manipulation of a first image behind the fixed target selection pattern by zooming and panning the first image. An inset frame in the corner of the screen shows the corresponding location in a second image. For example, if the user is picking a point on a user map image, it shows the selected digital map point. Conversely, if the user is selecting a digital map point, the inset shows the selected point on the map image. This approach has two drawbacks. First the user is required to switch between two point selection modes, one for the first image and one for the second image, which may look the same adding to user confusion. Second the user must compare the similarity of the location between the two images by referring to the main screen and an offset frame in the corner screen, which makes it more difficult to accurately match up relevant points on the two images.
Also, desktop image manipulation software may be used to align two digital images. Applications such as Adobe Photoshop allow users to create images that consist of multiple layers. A user may zoom, pan, and rotate each layer independently to align the images on each layer. The layer that is manipulated is usually selected from a separate menu outside the window displaying the layered image. A drawback to this approach is that it is often difficult to see which layer is selected when looking only at the image. This can result in accidental manipulation of the incorrect layer requiring the user to undo the changes and start again. This approach also requires the extra selection mechanism to select the layer to be manipulated, making it less than ideal for smaller screen devices.
Therefore, there is a need to develop a method of aligning digital images that overcomes the drawbacks of the above detailed methods. The need is especially great in the field of smart phones and other small mobile communications devices where screen real estate and ease of use are at a premium.